Vehicle seat heating arrangement

ABSTRACT

A vehicle seat having a heating device arranged in connection with the vehicle seat and connected to a control unit which includes a current-feeding apparatus for feeding a current to the heating device. The vehicle seat also includes a temperature sensor connected to the control unit for detecting the temperature at the heating device. The control unit is arranged to feed the current if the measured temperature falls below a pre-determined temperature value. An occupant sensor is also provided for detecting the presence of an occupant or an object in the vehicle seat. The occupant sensor is arranged as a single integral unit together with the heating device in the vehicle seat.

TECHNICAL FIELD

The invention relates to a vehicle seat arrangement comprising a heatingdevice arranged in connection with a vehicle seat and connected to acontrol unit which comprises current feeding means for feeding a currentto the heating device in order to heat it, a temperature sensorconnected to said control unit for detecting the temperature at saidheating device, the control unit being arranged to to feed said currentif said measured temperature falls below a predetermined temperaturevalue.

Furthermore, the invention relates to a method for manufacturing avehicle seat arrangement.

BACKGROUND OF THE INVENTION

For reasons of comfort and safety, today's vehicles are often providedwith electrically heatable vehicle seats. The driver's seat, as well asthe other seats in the vehicle, can be so arranged that they can beheated by means of heating elements in the form of electricallyconducting wires which can be placed in each seat in the shape of aheating coil. Such a heating element is normally placed in the back-restand the cushion of each seat when the seat is manufactured.

The heating element is furthermore connected to a current feeding unitwhich delivers current. In this manner, the heating element can beheated to a suitable temperature.

There is a requirement for each seat to have a carefully adjustedtemperature on its surface, i.e. on that surface which is in contactwith the person occupying the seat. For this purpose, the temperature ofthe heating element can be detected by means of a temperature sensorwhich is arranged in the seat, close to the heating element, and whichis connected to a central control unit. Using the temperature sensor andthe control unit, the temperature can be detected. The control unit alsocomprises current feeding circuits by means of which a certain currentcan be supplied to the heating element during a time period until acertain desired set value for the temperature is reached. The adjustmentof this set value can be done either by means of fixed resistances or bymeans of an adjustable potentiometer which is adjusted by the occupantof the seat in question.

Using the above-mentioned control method, current can be supplied to theheating element until the central control unit indicates (through theuse of said temperature sensor) that the set value has been reached.When this happens, the control unit will cut off the power feeding. Thiswill cause the heating element to cool down gradually. When the heatingelement has cooled so that its temperature again is below the set value,the power feeding will be resumed. The temperature control will continuein this manner as long as the system is operative.

The control of the supply of current to the heating element can beprovided in other ways, for example by means of a control unit which isintegrated in the vehicle (for example in the form of a control unitwhich normally is used for controlling the operation of the vehicle'sengine or for air condition control of the vehicle's compartment). Tothis end, such an external control unit can then be adapted so as tocommunicate with the above-mentioned heater control unit. Arrangementsfor such communication are previously known from the patent documents WO98/01798 and WO 98/01059.

Furthermore, in today's vehicles, it is common to use one or severalairbags for the protection of the occupants in the vehicle. In thisregard, there is a need for detecting the presence or absence of anoccupant in a seat which is associated with an airbag. In particular,there is a desire to detect the load acting upon the seat, in order toprovide an indication of the presence of an occupant or an object in aseat. The result of such detection can be used for activating ordeactivating various functions, for example said airbags. This is due tothe fact that an airbag for a passenger in the vehicle can cause severeinjuries if it is activated when, for example, a rearwards facingchild-seat is positioned in front of an airbag, or when a passenger whois not using a safety-belt leans forward at the moment of activation ofthe airbag. The result of such detection can be used for activatingother functions in a vehicle, in particular for providing headlightadjustments or a seat belt warning.

For this reason, it is previously known to equip a vehicle with a sensorarrangement which is arranged so as to provide an indication of whetheran occupant is present in a seat (which in turn is associated with anairbag) or an indication of whether an auxiliary child seat ispositioned on the seat. Also, the the orientation of the child seat orthe type of child seat being used is preferably determined. In thismanner, an airbag protection system in a vehicle can be deactivated if,for example, a child seat is placed on the seat in question. Thisconstitutes an advantage, since the risk for injuries to the personsitting in the child seat due to an activated airbag can be eliminated.

An arrangement for detection of the presence of a person or an object ina vehicle seat is previously known for example from the patent documentWO 98/14345. This invention concerns a method for determining severalparameters of a seated person. The evaluation of said parameters caninclude the estimation of the size and/or the weight of said person.

However, various problem may occur if a seat provided with a heatingelement as mentioned above were also to be equipped with a separatesensor for detecting the presence of an occupant in said vehicle.Firstly, it can be noted that the heating element can only be adhered toa particular section of the surface of the seat cushion where the sensoris not mounted. This allows a relatively limited area for the mountingof the heating element. Furthermore, there is a risk that the occupantsensor surface will come into contact with adhesion glue which is usedfor the heating element. This may cause prebending of the sensor, whichin turn may lead to deterioration of the detection signal from theoccupant sensor. Also, such an known arrangement would comprise a largenumber of components, which would lead to high costs for the seat.Furthermore, such an arrangement would imply a complex and costlyassembly of the seat, which would also lead to higher costs. Also, thereis a risk that the operation of the two components, i.e. the heatingelement and the occupant sensor, would be interfered since thecomponents are mounted very close to each other. Also, such an assemblyof a heating element and an occupant sensor would imply a risk that thesensor would slide out of position during its lifetime. Finally, such anassembly of a heating element and an occupant sensor would imply a riskthat the heating element would interfere with the operation of theoccupant sensor, i.e. the sensor may supply erroneous signals if is isheated.

Consquently, there are various problems involved when trying to combinethese two components within the same vehicle seat.

SUMMARY OF THE INVENTION

An object of the invention is to provide an improved vehicle seatarrangement by means of which the above-mentioned problems can besolved. This is accomplished by means of an arrangement of the kindinitially mentioned, which comprises a sensor for detecting the presenceof an occupant or an object in said vehicle seat, said sensor beingarranged as an integrated component together with said heating device inthe seat.

By means of the invention, several advantages can be accomplished.Firstly, it can be noted that the invention constitutes one singlepre-assembled unit which can be easily mounted in a vehicle seat duringmanufacturing thereof. Furthermore, with a common, integrated unit, itsadhesion to the surface of the vehicle seat can be made as large asnecessary since the occupant sensor will not need any separate adhesionpoints. Also, the problem involving a risk that the occupant sensorwould slide out of position in relation to the heating element can beeliminated by means of the invention.

The term “occupant presence sensor” (or “sensor”) is used in thefollowing to define a device for detecting the presence of an occupantor an object being positioned in a vehicle seat. This sensor can also beused for determining whether, for example, an auxiliary child seat isplaced in a particular vehicle seat. Consequently, this sensor isintended to provide a measuring signal which indicates whether said seatis occupied by a person or an object.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail for explanatory andin no sense limiting purposes with reference to the following drawings,in which:

FIG. 1 is a schematic diagram showing an arrangement according to thepresent invention,

FIG. 2 is a schematic diagram showing an arrangement generallycorresponding to FIG. 1 but in an assembled state, and

FIG. 3 is a perspective view of an integrated arrangement according tothe invention.

PREFERRED EMBODIMENTS

FIG. 1 shows a schematic and slightly simplified circuit diagram of anarrangement according to the present invention. According to thepreferred embodiment, the invention is intended for use in connectionwith an electrically heatable seat 1 in a vehicle.

FIG. 1 shows the main components forming part of the invention, whichgenerally constitutes an integrated heating and occupant presencedetection system. According to a preferred embodiment, said arrangementcomprises a seat heating device 2 and an occupant presence sensor 3,which in FIG. 1 are shown in a separated manner, but are intended to beassembled and arranged as an integrated component to be placed in apredetermined area 4 in the vehicle seat 1.

It should be noted that the invention is not limited to any particulartype of vehicle seats, but can be used in cars, buses, trucks or othertypes of vehicles in which a heatable seat can be used.

The heating device 2 will now be described in detail. The heating device2 comprises a carrier layer 5 in the form of a generally thin andflexible sheet of fabric or a similar material. The carrier layer 5supports a heating element 6 in the form of a electrically conductingwire. The heating element 2 is, as such, of a previously known kind, andforms a heating coil which is defined by the electrical resistance ofthe conducting wire. Preferably, the wire is woven into the carrierlayer 5, according to a layout which is adapted to the heatingrequirements of the seat 1 in question. However, the heating wire can bemounted in other ways, for example by providing two carrier layersinstead of one. In such a case, the heating wire is then placed betweenthese two layers. Alternatively, the heating wire may also be usedwithout any carrier layer.

The heating element 2 is intended to be arranged inside the vehicle seat1, preferably in its cushion. In principle, the heating element 2 canalso be placed in the back-rest of the seat 1. Although the figure showsonly one heating element 2, it is possible to connect several suchelements to the control unit 1, for example in the form of a separateheating element for the cushion of the seat and a heating element forthe backrest of the seat.

The heating element 6 is terminated by two terminals 7, 8 which areintended to be connected to a control unit 9, which is arranged in asuitable place in the vehicle and connected to the terminals 7, 8 viacorresponding electrical conductors.

In a manner which is known per se, the control unit 9 is arranged tofeed a certain current I through the heating element 5 in order to heatthe seat 1. This operation will be described in detail below.

It should be noted that FIG. 1 shows the invention in a slightlysimplified form. Consequently, the figure does not show all of thecomponents of the control unit 9, but only those parts which arenecessary for the understanding of the invention.

Furthermore, in the vicinity of the heating element 2 there is arrangeda temperature sensor 10 which is electrically connected to the controlunit 9. The temperature sensor 5 is preferably in the form of athermistor of the NTC kind (“Negative temperature coefficient”), whichhas a temperature depending resistance R which corresponds to thetemperature T which is present in the vicinity of the heating element 2.Alternatively, a temperature sensor of the PTC kind (“Positivetemperature coefficient”) temperature sensor can also be used, or anyother type of sensor which supplies a signal which istemperature-dependent.

There is furthermore a current source 11 connected to the control unit 9via a further connection. The current source 11 is preferablyconstituted by the starting battery of the vehicle. The systemfurthermore comprises an on/off switch (not shown) which for example isintegrated in the ignition lock of the vehicle. The switch is arrangedso that the control unit 9 is activated when the switch is closed. Theswitch can alternatively be constituted by a control function which isprovided by the control unit 9. In such case, the switch can beactivated for example as a result of a door lock sensor (not shown)indicating that at least one door of the vehicle has been opened. Inthis manner, the heating of the heating device 2 can be activated beforethe vehicle is started, preferably even before the seat is occupied.

In the following, the general design and main functions of the controlunit 9 will be described. The control unit 9 comprises a logic unit,which preferably is computer based, but which can also consist ofpreviously known electronics circuits. The logic unit is arranged toestablish an indication of the temperature T in the seat 1, as detectedby means of the temperature sensor 10. This detection preferablyutilizes a measuring bridge of the Wheatstone-bridge type (not shown)which is arranged so that the logic unit can calculate a valuecorresponding to the present temperature T. The detection canalternatively be carried out by means of any other suitable measuringbridge circuit.

Furthermore, the control unit 9 comprises a switch unit (not shown)which feeds the current I through the heating element 2 depending onsignals from the above-mentioned logic unit. The switch unit ispreferably based on a MOSFET transistor, which is a semi-conductorcomponent which can efficiently deliver large currents from the currentsource 11 to the heating element 6 and which can also be used so as tocontrol the current between the current source 11 and the heating device2. Alternatively, the switch unit can be formed in other ways, forexample by means of other types of transistors or a relay.

The logic unit of the control unit 9 is thus arranged to determine avalue of the current temperature T. If the temperature T is lower than apreset value T_(A) which corresponds to a certain desired temperature onthe surface of the vehicle seat 1, the logic unit will control theabove-mentioned switch unit to deliver the current I to the heatingelement 6. When the set value T_(A) is reached, the logic unit switchesoff the feeding of current to the heating element 6 by means of theswitch unit.

The invention is not limited to the above-mentioned type of currentcontrol in order to regulate the heating. Alternatively, the control ofthe heating can be based on a regulation of the voltage level of theheating wire.

Furthermore, as mentioned above there is provided an occupant presencesensor 3 which is arranged as an integrated part of the combined heatingdevice and occupant sensor arrangement according to the invention. Tothis end, the sensor 3 comprises a support element in the form of acarrier layer 12 which is a generelly thin and flexible sheet of asuitable plastics material, preferably PET. However, the invention isnot limited to the use of PET, but other materials such as for examplePI, PEM or any other suitable material, preferably a plastics material,can also be used.

The carrier layer 12 supports a plurality of force-sensing elements 13which are positioned as an array or a matrix on the carrier layer 12.Each of the force-sensing elements 13 comprises a force-sensingcomponent or material, in a manner which is known per se. Furthermore,the elements 13 are electrically intereconnected by means of electricalconductors (not shown in FIG. 1) which are terminated by a number ofterminals, of which two terminals 14, 15 are indicated in FIG. 1 in aschematical manner. Said terminals 14, 15 are connected to a secondcontrol unit 16 via electrical conductors. The second control unit 16,which preferably is powered by the above-mentioned current supply 11, isarranged so as to provide a measurement of the force distribution actingupon the seat 1, by means of the signals from each of the force-sensingelements 13. By comparing the measured force distribution withpredetermined force distribution patterns being stored in the secondcontrol unit 16, the second control unit 16 can provide an output signalwhich indicates whether a person or an object is positioned in the seat1. In the event that an airbag (not shown) is associated with the seat1, said output signal can be used for example for allowing or preventingthe actuation of the airbag. Said output signal can also be used todetermine how the occupant or the object is positioned in the seat, forexample whether a person is leaning forward or backward in the seat.

The invention is particularly, but not exclusively, intended to be usedfor detecting the absence or presence of a person with reference to adefined detection area in the seat of a vehicle. The detection can, forexample, be utilized in systems the purpose of which is to deactivate anair-bag if a passenger is not present in the detection area. Thisprevents the air-bag from being triggered unnecessarily or from causinginjuries due to the fact that a child seat is placed in the seat of thevehicle, or that the passenger sits in a non-suitable position in theseat of the vehicle. For this purpose, the detection area is suitablychosen to comprise a limited part of the area at the seat 1, so thatpresence does not only mean that a person is present in the seat, butfor presence to be detected the person must also sit essentiallyreclined in the seat, or at a certain maximal distance from theback-rest. This means that when a child seat is placed in the seat witha child sitting in the seat, absence is detected and a correspondingairbag will not be actuated in the event of a collision.

The occupant presence sensor 3 according to the invention canalternatively be used for actuating the heating device 2. This isparticularly advantageous if only a limited amount of electric power isavailable for the heating device. According to such an embodiment, thetwo control units 9, 16 as described above are preferably integratedinto one single unit. Also, in this case, such a control unit would thenbe arranged so as to allow actuation of the heating device 2 only when aperson is sitting in the seat 1.

FIG. 2 shows a perspective view corresponding to that of FIG. 1, butwith the heating device 2 and the occupant presence sensor 3 arranged intheir assembled state. The invention relies on the fact that the heatingdevice 2 and the occupant presence sensor 3 are arranged as twocomponents which are assembled in a laminated manner, so as to form anintegrated unit. For this reason, the occupant presence sensor 3 is notfully visible in FIG. 2, since the heating device 2 is positioned abovesaid sensor 3. In particular, these components are preferablyprefabricated or pre-assembled so as to form one single unit which isintended to be mounted in a vehicle seat during manufacturing of theseat.

According to the preferred embodiment of the invention, the heatingdevice 2 and the occupant presence sensor 3 are assembled by means ofgluing or ironing. More precisely, the heating device 2 may thencomprise one or two carrier layers which are provided with glue. Theselayers are laminated either by using only one carrier layer, on theupper side of the sensor, or with two carrier layers, i.e. one on eachside of the sensor. When using two carrier layers, both of them can haveglue, or only the carrier layer with the heating wire can be providedwith glue.

Furthermore, a protective layer can be placed between the occupantsensor and the heating wire, i.e. inside the complete sandwichcomponent. Such a protective layer can be manufactured from a suitablefoam, felt or fabric material.

Furthermore, the heating wire 6 can in principle also be arrangeddirectly on the occupant sensor surface (i.e. the surface of the sensorcarrier layer 12), for example by gluing it directly on said surface.

The two control units 9, 16 (see also FIG. 1) can preferably be combinedin a common housing with or without a common logic unit. In this manner,the heating control components using the detection of the temperatureand the signal from the occupant presence sensor 3 will then beaccommodated in one single unit. This combined unit can furthermore beprovided with a common communication system which then may communicatewith an external computer system in the vehicle.

Any one of the two control units 9, 16, or the above-mentioned single(i.e. combined) control unit, can be placed on the heating device 2 orthe occupant sensor 3. Preferably, such a control unit is thenpreferably crimped on the carrier layer 12 of occupant sensor.

Furthermore, the temperature sensor 10 can be placed on the heatingdevice 2, as mentioned above. Alternatively, the temperature sensor 10can be placed on the surface of the occupant sensor 3 (i.e. on thesurface of its carrier layer 12) and the signal from the temperaturesensor 10 can be used to control the heating element, as mentionedabove.

More than one temperature sensor can be used. By placing severaltemperature sensors along the surface of the occupant sensor carrier 12,temperature signals from various areas of the vehicle seat surface cancan be used to improve the operation of the occupant sensor. Forexample, by using the temperature in occupant sensor function,differences in the stiffness of the vehicle seat foam can be compensatedfor. In this manner, a more accurate signal can be obtained.

Furthermore, the heating element 2 can be operated so as to heat thepressure points 13 of the occupant sensor 3. Preferably, the seat isheated slightly (i.e. above approximately 10° C.).

According to a particular embodiment of the invention, the heating ofthe heating device 2, i.e. the supply of heating current to the heatingwire 6, is preferably synchronized with the measurement cycles of theoccupant sensor 3, i.e. it is synchronized with the occasions at whichmeasurement signals are supplied from said sensor 3. This means that,for example, the heating device 2 can be controlled so that it isswitched off just before each point in time at which a measurementsignal is being fed from the occupant sensor 3. By switching off theheating device 2, the heating wire 6 is allowed to cool down. This leadsto a situation in which the occupant sensor 3 is given an essentiallyuniform temperature at every occasion when measurement signals aresupplied from the occupant sensor 3. In this manner, any risk ofinterference from the heating device 2 during measurements with theoccupant sensor 3 can be eliminated, which is an additional advantagewith the present invention.

FIG. 3 shows in a schematical form the design of the integrated heatingelement and occupant sensor according to the invention. In this regard,FIG. 3 shows the various layers and components which can be usedaccording to a preferred embodiment. In particular, the combinedarrangement according to the invention comprises a first layer 5 orcarrier layer which corresponds to the carrier layer described above andshown in FIG. 1. A heating wire 6 is mounted on the underside of saidfirst layer 5 in a suitable manner, for example by weaving it into thefirst layer 5 or by gluing it onto the first layer 5.

The mounting of the heating wire 6 can be accomplished through the useof a second layer 17. In this manner, the heating layer 6 will bearranged between the first layer 5 and the second layer 17. In thiscase, no glue is necessary on the heating wire 6. Instead the two layers5, 17 can be glued together (the heating wire 6 then being positionedinbetween) by providing glue on the underside of the first layer 5(and/or by providing glue on the top side of the second layer 17).

An advantage with the second layer 17 is that it constitutes aprotective layer which is arranged between the heating wire 6 and theoccupant presence sensor 3 (cf. FIG. 1). In this manner, the heatingwire 6 is protected from direct contact with the pressure-sensingelements 13 on the occupant presence sensor 3.

As an additional protection, a third layer 18 can be provided under thesensor carrier layer 12. However, this is not necessary in allapplications.

When manufacturing the arrangement according to the invention, all thesuitable layers (if any) are combined with the heating wire 6 and thepresence sensor 3 into an integrated, laminated assembly whichsubsequently can be mounted in a vehicle seat as a single unit duringmanufacturing thereof.

The invention is not limited to the embodiments described above but maybe varied within the scope of the appended patent claims. For example,the invention can be arranged in various ways, for example with orwithout each one of the three layers 5, 17, 18. Furthermore, theoccupant sensor can be in the form of a pressure sensor operating eitherdirectly with pressure (compressing the sensing area) or with bending(bending the sensing area). Other types of sensors are also possible,for example capacitive sensors, which are used so as to detect theinfluence of a human being on electrical fields in the vehicle.

Also, as opposed to what is shown in FIG. 1, in which the heating device2 is arranged on top of the occupant presence sensor 3, the inventioncan alternatively be accomplished by arranging the occupant presencesensor 3 on top of the heating device 2.

Furthermore, the invention can be implemented with or without theprotective layers 17, 18 shown in FIG. 3. Also, the heating wire can bearranged underneath or on top of the carrier layer 5 shown in FIG. 1.Also, it is possible to use a layer of the heating device to supportoccupant sensing elements such as the sensing elements 13 describedabove.

1. A vehicle seat comprising: a heating device arranged in connectionwith a vehicle seat and connected to a control unit, said control unitincluding current feeding means for feeding a current to said heatingdevice; a temperature sensor connected to said control unit, saidtemperature sensor adapted for detecting a temperature at said heatingdevice, said control unit being operative to feed said current if adetected temperature falls below a predetermined temperature value; andan occupant sensor for detecting the presence of an occupant or anobject in said vehicle seat, said occupant sensor being arranged as anintegrated component together with said heating device in said vehicleseat, wherein said occupant sensor and said heating device are formed astwo laminated sheet layers.
 2. The vehicle seat according to claim 1,wherein said heating device and said occupant sensor are prefabricatedas one single integrated unit adapted to be mounted in said vehicleseat.
 3. The vehicle seat according to claim 1, further comprising aprotection material disposed between said occupant sensor and saidheating device.
 4. The vehicle seat according to claim 1, wherein saidheating device includes a carrier layer and a heating wire, said heatingwire being arranged on said carrier layer.
 5. The vehicle seat accordingto claim 1, wherein said heating device includes two carrier layers anda heating wire, said heating wire being arranged between said twocarrier layers.
 6. The vehicle seat according to claim 1, wherein saidoccupant sensor includes a carrier layer and a plurality ofpressure-sensing elements, said pressure-sensing elements being arrangedon said carrier layer.
 7. The vehicle seat according to claim 6, whereinsaid heating device includes a heating wire, wherein said carrier layersupports said heating wire and forms part of said heating device.
 8. Thevehicle seat according to claim 7, wherein said carrier layer is made ofa plastic material.
 9. The vehicle seat according to claim 7, whereinsaid control unit is arranged on said occupant sensor.
 10. The vehicleseat according to claim 6, wherein said carrier layer is made of aplastic material.
 11. The vehicle seat according to claim 6, whereinsaid control unit is arranged on said occupant sensor.
 12. The vehicleseat according to claim 1, wherein said control unit for said heatingdevice also comprises control unit for said occupant sensor.
 13. Thevehicle seat according to claim 1, wherein said temperature sensor isused for the control of the operation of said occupant sensor.
 14. Thevehicle seat according to claim 1, wherein said heating device isoperative so as to provide heat in response to a signal from saidoccupant sensor.
 15. The vehicle seat according to claim 1, wherein saidoccupant signal outputs a signal upon detecting the presence of anoccupant or an object in said vehicle seat, wherein said control unit isadapted to switch said heating device on and off in a synchronizedmanner with respect to the occasions at which said signal is outputtedfrom said occupant sensor.
 16. A method for manufacturing a vehicleseat, comprising the steps of: providing a heating device; providing anoccupant sensor for detecting the presence of an occupant or an objectin a vehicle seat; and providing a temperature sensor adapted to beconnected to a control unit, said control unit adapted for detecting atemperature at said heating device, said control unit being operative tofeed a current to said heating device if a detected temperature fallsbelow a predetermined temperature value; wherein said heating device andsaid occupant sensor are provided as an integrated component and formedas two laminated sheet layers.
 17. The method according to claim 16wherein said control unit is mounted on said occupant sensor.
 18. Themethod according to claim 16, further comprising providing a protectionmaterial between said occupant sensor and said heating device.
 19. Themethod according to claim 18, wherein said control unit is mounted onsaid occupant sensor.
 20. A vehicle seat comprising: a heating devicearranged in connection with a vehicle seat and connected to a controlunit, said control unit including current feeding means for feeding acurrent to said heating device; a temperature sensor connected to saidcontrol unit, said temperature sensor adapted for detecting atemperature at said heating device, said control unit being operative tofeed said current if a measured temperature falls below a predeterminedtemperature value; and an occupant sensor for detecting the presence ofan occupant or an object in said vehicle seat, wherein said occupantsensor and said heating device are assembled so as to form a singleintegral unit, such that said occupant sensor and said heating deviceare attached to one another.
 21. The vehicle seat according to claim 20,wherein said occupant sensor and said heating device are assembled toone another with glue.
 22. The vehicle seat according to claim 20,further comprising a protection material disposed between said occupantsensor and said heating device.
 23. The vehicle seat according to claim20, wherein said heating device includes a carrier layer and a heatingwire, said heating wire being arranged on said carrier layer.
 24. Thevehicle seat according to claim 20, wherein said occupant sensorincludes a carrier layer and a plurality of pressure-sensing elements,said pressure-sensing elements being arranged on said carrier layer. 25.The vehicle seat according to claim 20, wherein said control unit forsaid heating device is also comprises a control unit for said occupantsensor.
 26. The vehicle seat according to claim 20, wherein said heatingdevice is operative so as to provide heat in response to a signal fromsaid occupant sensor.
 27. The vehicle seat according to claim 20,wherein said occupant sensor outputs a signal upon the presence of anoccupant or an object in said vehicle seat, wherein said control unit isadapted to switch said heating device on and off in a synchronizedmanner with respect to the occasions at which said signal is outputtedfrom said occupant sensor.
 28. A method of manufacturing a vehicle seat,comprising the steps of: providing a heating device, providing anoccupant sensor for detecting the presence of an occupant or an objectin a vehicle seat; providing a temperature sensor, said temperaturesensor being adapted to be connected to a control unit, said controlunit adapted for detecting a temperature at said heating device, saidcontrol unit being operative to feed a current to said heating device ifa detected temperature falls below a predetermined temperature value;and assembling said heating device and said occupant sensor in the formof a single integral unit such that said heating device and saidoccupant sensor are attached to one another.
 29. The method ofmanufacturing a vehicle seat according to claim 28, wherein saidoccupant sensor and said heating device are attached to one another withglue.
 30. The method of manufacturing a vehicle seat according to claim28, further comprising providing a protection material between saidoccupant sensor and said heating device.
 31. A vehicle seat comprising:a heating device arranged in connection with a vehicle seat andconnected to a control unit, said control unit including current feedingmeans for feeding a current to said heating device; a temperature sensorconnected to said control unit, said temperature sensor adapted fordetecting a temperature at said heating device, said control unit beingoperative to feed said current if a measured temperature falls below apredetermined temperature value; and an occupant sensor for detectingthe presence of an occupant or an object in said vehicle seat, whereinsaid occupant sensor and said heating device are assembled so as to forma single integral unit, such that said occupant sensor and said heatingdevice are attached to one another; wherein said occupant sensorincludes a carrier layer and a plurality of pressure-sensing elements,said pressure-sensing elements being arranged on said carrier layer. 32.The vehicle seat according to claim 31, further comprising a protectionmaterial disposed between said occupant sensor and said heating device.33. The vehicle seat according to claim 31, wherein said heating deviceincludes a carrier layer and a heating wire, said heating wire beingarranged on said carrier layer.
 34. The vehicle seat according to claim31, wherein said heating device includes two carrier layers and aheating wire, said heating wire being arranged between said two carrierlayers.
 35. The vehicle seat according to claim 31, wherein said controlunit for said heating device is also comprises a control unit for saidoccupant sensor.
 36. The vehicle seat according to claim 31, whereinsaid heating device is operative so as to provide heat in response to asignal from said occupant sensor.
 37. The vehicle seat according toclaim 31, wherein said occupant sensor outputs a signal upon thepresence of an occupant or an object in said vehicle seat, wherein saidcontrol unit is adapted to switch said heating device on and off in asynchronized manner with respect to the occasions at which said signalis outputted from said occupant sensor.